#ifndef _BIEUTHUC_H
#define _BIEUTHUC_H
#include <string>
#include <sstream>
#include <iostream>
using namespace std;


// Dinh nghia Lop BieuThuc
class BieuThuc{
private:
	BieuThuc* bieuThuc;
protected:
	BieuThuc();
	//~BieuThuc();
	virtual BieuThuc* timDaoHam() = 0;
public:
	virtual double tinhGiaTri(double x) = 0;
	virtual BieuThuc* tinhDaoHam(); 
	virtual void daoDauBieuThuc() = 0;
	virtual string xuatChuoi() = 0;
};
#endif